Garden Loosestrife Lysimachia Vulgaris Class B Noxious Weed in WA State, Regulated in King County

The latest on the emergent noxious weed Garden Loosestrife (Lysimachia vulgaris) in King County

Ben Peterson

King County Noxious Weed Control Program Talk outline

• Garden loosestrife identification • Garden loosestrife distribution and impacts • Un-successful control methods • Our in-situ herbicide study • Suggestions Garden Loosestrife Lysimachia vulgaris Class B Noxious Weed in WA state, regulated in King County

2-10 foot tall perennial of wetlands and shorelines Native to Eurasia Flowers: showy yellow primrose-like flowers clustered at top of stem (terminal pannicle) Each flower: 5 sepals, 5 pedals Flowers in July to September Leaves: opposite or whorled (in threes or fours), leaves usually have small orange or black glands visible with magnification garden loosestrifegarden Produces extensive red rhizomes that will reach out up to 10 feet into the adjacent open water Stems have soft hairs and are round, occasionally flattened (fasciated) garden loosestrifegarden Reproduces by both rhizome…

• Rhizome pieces as short as 1 and 2 cm in length can produce shoots. -Kelsey Taylor, (2017), Competitive Interactions and Rhizome Reproductive Capacity of an Invasive Plant, Garden Loosestrife (Lysimachia vulgaris L.), Unpublished Masters Thesis, University of Washington, Seattle, WA. garden loosestrifegarden

…and by seed. • Seeds average 82% viability when exposed to summer temperatures

-Kevin Dillon 2012, Senior research project on seed viability, School of Environmental and Forestry Science, University of Washington

Garden loosestrife seeds garden loosestrifegarden How tall does it get in King County?

10’ Shade Flora of China 2-4 ft University of Wisconsin to 3.3 ft Connecticut Botanical Society 2-4 ft England 2-4 ft Germany 1.4-4.9 ft Australia to 4.9 ft Flora of Europe to 4 ft 6’6” Full sun Karen is actual size actual is Karen garden loosestrifegarden what garden loosestrife isn’t: purple loosestrife( Lythrum yellow loosestrife (Lysimachia salicaria), punctata), Same Genus • a different Order and Family • Star-shaped flowers occur all along • Square stem the stem only (never in a terminal • Purple/magenta flowers cluster like L. vulgaris) Heidi Bonhan L. vulgaris (garden) and L. punctata (yellow) together garden loosestrifegarden Garden loosestrife distribution in Washington

Lake Whatcom

Loon Lake Garden Loosestrife Distribution in King County, WA 2018 First found in 1978

Study site garden loosestrifegarden Garden loosestrife Impacts Ecological – displaces native plants and animals; interferes with wetland food web and habitat; clogs small streams

Economic – clogs irrigation systems & water control structures; dominates wet pastures garden loosestrifegarden Garden Loosestrife - Impacts Outcompetes other plants, even tough ones

With purple loosestrife

Even Himalayan With common blackberry cattail garden loosestrifegarden Why so aggressive in King County? Could it be polyploid?

• Polyploidy = inheriting more than the usual 2 copies of DNA (2n = normal vs. 3n=polploid) • Polyploid plants = potentially more genetically diverse and able to grow more aggressively • Rhizomes were collected from three sites in the county in June 2011 (Lake Sammamish, Rutherford Slough, Lake Burien) • Analyzed by Brenda Grewell at USDA-ARS University of California, Davis • All samples came back as 2n – not polyploid garden loosestrifegarden Control - what doesn’t work so well

Manual: Really only feasible for individuals or pioneering stands; could dig out as much root as possible; this plant doesn’t pull well (breaks off from long rhizomes leaving lots of root behind).

Mechanical: Repeated mowing may keep it contained and slow dispersal by seed, but won’t kill it. Plant fragments will root if left behind. garden loosestrifegarden Control - Cultural

• Weed fabric or tarp recommended to suppress plants on sensitive shorelines, but won’t kill mature plants. • Potentially useful in small area without moving water • Requires careful monitoring, high maintenance garden loosestrifegarden Cultural: Tarp over garden loosestrife plants at Oxbow Farm

• Heavy opaque tarp • Stake down corners well • Lay debris (wood) over top • Check in July and September for : • Tarp integrity • Sneaky plants

Plants growing through rip in tarp garden loosestrifegarden Control – Biocontrol? Jennifer Andreas Jennifer - Photo garden loosestrifegarden Control – Biocontrol? • A insect has been found eating some garden loosestrife plants • Identified as a sawfly (Monostegia abdominalis) –Chris Looney, WSDA • Insect is non-native, but not intentionally released = not biocontrol • Unknown impact - plants still flower and set seed even if skeletonized • Actual biocontrol development unlikely until the plant becomes a “problem” in more places Jennifer Andreas Jennifer - Photo garden loosestrifegarden Control – Chemical (herbicide) • Needs to be systemic – to get at those rhizomes • Needs to be an aquatic –approved herbicide • Have tried many herbicides over the years: • Triclopyr –seems to act too fast, plants return • Glyphosate- not complete kill • Imazapyr – works pretty well, acts very slowly, off target damage • Imazamox? • Combinations of herbicides? garden loosestrifegarden Greenhouse study

• Conducted by Tim Miller* at WSU Extension Mt. Vernon • Rhizomes collected and potted-up May 2014 • Grown for 6 weeks in greenhouse • Treated with both single and Tim Miller combinations of herbicides • Herbicide allowed to be active for one month, then defoliation rated and plants clipped • After two months, regrowth measured

*[email protected] Tim Miller garden loosestrifegarden

Garden Loosestrife Regrowth

Biomass (g) 2 Months After Treatment garden loosestrifegarden Greenhouse study results

• Imazapyr at 0.75% • Imazapyr at 0.5% + Triclopyr at 1% • Imazamox at 0.5% + Triclopyr at 1% • Glyphosate at 1% + aminopyralid* at 0.25%

*not aquatic-approved, Tim Miller don’t exceed label rate garden loosestrifegarden Field Study Methods • Lake Sammamish shoreline study site • “pristine” garden loosestrife plants in 400m section of shoreline • 30 - 3m x 3m study plots set up, min. 2m between plots • Garden loosestrife stems/plot • Average & maximum stem height • Phenological state at time of treatment • List of other plants growing in plot and site conditions garden loosestrifegarden Field Study Methods • Focus on imazamox in effort to reduce un-intended harm to other plants such as willow (that seem particularly sensitive to imazapry) • Foliar spray herbicide treatments*: Treatment Imazamox Triclopyr TEA Glyphosate Surfactant (Agri-dex) T-1 3% 0.5% - 1% T-2 2% 1% 1% T-3 4% 1% 1% T-4 4% 1% C (control) No herbicide No herbicide No herbicide No herbicide Pre-flower *percent = volume chemical/volume total mix including water flowering

• Two treatment dates: • Early treatment – June 22 (all plants pre-flower stage) • Late treatment – August 10 (all plants flowering stage) garden loosestrifegarden

Results were measured 12 months later (7/19/18) • Counted garden loosestrife stems, • Some missing or disturbed plots (vandalism, big trees fallen over) • Un-even sample site, very few replicates • Data analysis help from Tim Miller* (he squeeze some results from our very messy data) *WSU extension Mt. Vernon

A “control” study plot A herbicide study plot garden loosestrifegarden

Average stem height (cm) 1 year after treatment 120

a 100

80 b 60 bc 40 bc c 20

0 11 22 33 4 Controlcontrol 3% imazamox 2% imazamox 4% imazamox 4% imazamox 0.5% triclopyr TEA 1% glyphosate 1% glyphosate -20 garden loosestrifegarden

Percent control- 1-year after treatment 100

0 1 2 3 4 3% imazamox 2% imazamox 4% imazamox 4% imazamox 0.5% triclopyr TEA 1% glyphosate 1% glyphosate -20 avg. percent control June August (P value = 0.07) (not significantly different, sample size too small) garden loosestrifegarden Results Summary • Best – Treatment 3 (4% imazamox + 1% glyphosate) in June • Second best – Treatment 2 (2% imazamox + 1% glyphosate) in June and August – Treatment 4 (4% imazamox) in August • Third best – Treatment 3 (4% imazamox + 1% glyphosate) in August * – Treatment 4 (4% imazamox) in June • Triclopyr TEA hindered imazamox effectiveness • 23% of study plots = some off-target damage to woody plants

* suspect poor data from one of these study plots as a result of plot damage garden loosestrifegarden

Overall treatment recommendations

• Still no prefect treatment • Very small areas= long term tarping or deep, persistent digging • 1% imazapyr (where no woody native spp.)- late summer • 4% imazamox (w or wo/1% glyphosate) (where woody native spp.) – early summer (pre-flower) to avoid insect pollinators – Late summer (flowering) also effective • Try aminopyralid in sites where allowed • Persistence (go back annually, don’t let it seed) garden loosestrifegarden Suggestions for future studies

• Many more replicates • Avoid informal beaches • Potted plant study (with mature plants) • More herbicide combinations • Try different surfactants garden loosestrifegarden

August 2003

Flowering garden loosestrife Garden Loosestrife at Rutherford Slough (Fall City, WA)

• Herbicide treatment almost August 2014 every year since 2003 • Glyphosate or triclopyr 2003-2010 • Imazapyr 2012 and 2013 • Glyphosate + triclopyr 2014

Eric Meador Thank You Jennifer Andreas Kelsie Crawford Jordan Drugge Ellison Heil Elby Jones Kirk Massee Katie Messick Tim Miller Kelsey Taylor King County Noxious Weed Control Program

[email protected]